1. Field of the Invention
The present invention relates to an air bag system mounted in a vehicle, and more particularly to a cushion for air bag systems which is capable of preventing breakage of sewn parts of the cushion caused by means of expansion pressure of the cushion when a collision of the vehicle occurs.
2. Description of the Related Art
Generally, an air bag system for vehicles is mounted in front of a driver seat or a passenger seat in such a manner that a cushion of the air bag system is instantly expanded when a collision of the vehicle occurs for protecting a driver or a passenger from injury.
The air bag systems may be classified into a driver air bag system and a passenger air bag system. The driver air bag system is mounted to the steering wheel of the vehicle for protecting the driver from injury. The passenger air bag system is mounted to an instrument panel of the vehicle disposed in front of the passenger seat for protecting the passenger from injury. Basically, the driver air bag system is requisite, and the passenger air bag system is optional; however, vehicles with passenger air bag systems basically mounted therein for protecting passengers from injury are on the increase in recent years.
FIG. 1 is a cross-sectional view showing a passenger air bag system according to the conventional art, FIG. 2 is a perspective view showing the passenger air bag system according to the conventional art, FIG. 3 is a perspective view showing a cushion of the passenger air bag system according to the conventional art, and FIG. 4 is a plan view showing an inlet part of the cushion of the passenger air bag system according to the conventional art.
As shown in FIGS. 1 and 2, the conventional passenger air bag system for vehicles comprises: an air bag housing 4 mounted in an instrument panel 2; an inflator 6 attached to the air bag housing 4 for discharging gas when a collision of the vehicle occurs; a retainer 8 attached to the inside of the air bag housing 4 and having a plurality of gas-discharging holes for discharging gas from the inflator 6; and a cushion 10 accommodated in the air bag housing 4 such that the cushion 10 is expanded toward a passenger seat by means of gas discharged through the air-discharging holes of the retainer 8, the cushion 10 being fixed to the retainer 8 at one side thereof.
The air bag housing 4 comprises: a cushion housing 12 attached to the rear part of the instrument panel 2, the cushion housing 12 being formed in the shape of a box with the front part opened so that the cushion 10 is accommodated in the cushion housing 12; and a can housing 14 connected to the rear part of the cushion housing 12, wherein the inflator 6, which supplies high-pressure gas to the cushion 10 when a collision of the vehicle occurs, is disposed in the can housing 14.
The cushion housing 12 is provided at both longitudinal sides thereof with flanges 12a, respectively, which are fixed to the instrument panel 2 by means of bolts. The can housing 14 is provided at the outside thereof with a mounting bracket 16, which is fixed to a cowl cross member 18 by means of a bolt.
The inflator 6 is connected to a collision-detecting sensor (not shown) for detecting a collision of the vehicle so that the inflator 6 is exploded by means of a signal outputted from the collision-detecting sensor when the collision of the vehicle occurs. The cushion 10 is expanded toward the front of the cushion housing 12 by means of gas having a prescribed pressure, which is generated from the explosion of the inflator 6.
The instrument panel 2 is broken along a cut line 2a formed at the instrument panel 2 by means of the cushion 10 expanded as described above. Consequently, the cushion 10 is expanded toward the passenger seated in the passenger seat of the vehicle.
As shown in FIGS. 3 and 4, the cushion 10 comprises: a main panel 22 formed in the shape of a cylinder and having an inlet part 20 formed at one side thereof, the inlet part 20 of the main panel 22 being fixed by means of the retainer 8; side panels 24 attached to both open sides of the main panel 22 by means of sewing, respectively; and a tether 26 having one end fixed to the inlet part 20 of the main panel 22 and the other end fixed to the inner side of the panel 22, which is opposite to the inlet part 20 of the main panel 22.
The main panel 22 is formed in such a manner that a long strip is rolled in the shape of a cylinder and then stitched. The main panel 22 is the front part of the cushion 10, which approaches a passenger when the cushion 10 is expanded. To the sides of the main panel 22 are attached the side panels 24 by means of a first sewing part 28, respectively.
Each of the side panels 24 has a ventilation hole 24a formed at a prescribed part thereof for discharging gas introduced into the cushion 10 to the outside. When the passenger contacts the cushion 10 due to the impact caused when a collision of the vehicle occurs, the gas in the cushion 10 is discharged to the outside through the ventilation hole 24a so that shock transmitted to the passenger is effectively absorbed.
The tether 26 is formed in the shape of a long strip. One end of the tether 26 is fixed to the inlet part 20 of the main panel 22 by means of a second sewing part 30. The other end of the tether 26 is fixed to the inner side of the front part of the main panel 22 opposite to the inlet part 20 of the main panel 22, by which the shape of the expanding cushion 10 is determined.
One end of the tether 26 with the above-stated construction is fixed to the inlet part 20 of the main panel 22 so that the tether 26 forms the inlet part 20 together with the main panel 22. The inlet part 20 of the main panel 22 is provided at the center thereof with a gas-introducing hole 20a, which communicates with the gas-discharging holes of the retainer 8 for introducing the gas discharged from the inflator 6 into the cushion 10. Around the gas-introducing hole 20a formed at the inlet part 20 of the main panel 22 are formed a plurality of fixing holes 20b, through which the inlet part 20 of the main panel 22 is attached to the can housing 14 along with the retainer 8 by means of bolts.
Especially, one end of the tether 26 is formed with the same width as the inlet part 20. Both sides of the tether 26 are sewn with the main panel 22 and the side panels 24, by which the first sewing part 28 is formed. The second sewing part 30 is formed in the lateral direction of the tether 26 so that the first and second sewing parts 28 and 30 intersect each other at both sides A of one end of the tether 26.
Alternatively, one end of the tether 26 may be fixed to the main panel 22 by means of sewing while not forming the inlet part 20 together with the main panel 22. In this case, it is required to attach a plurality of additional reinforcing cloths to the main panel 22 so that the strength of the inlet part 20 is increased.
Preferably, the tether 26 and the main panel 22 together form the inlet part 20. Consequently, durability and thermal resistance of the inlet part 20 are increased by means of the tether 26, which requires no reinforcing cloths or only a reduced number of reinforcing cloths.
The operation of the conventional passenger air bag system with the above-stated construction will now be described. When a collision of the vehicle is detected by means of the collision-detecting sensor, a signal outputted from the collision-detecting sensor is transmitted to the inflator 6 so that the inflator 6 is exploded to generate gas.
The gas generated by means of the inflator 6 flows along the air bag housing 4 so that the gas is supplied to the gas-discharging holes of the retainer 8 and the inlet part 20 of the cushion 10. The gas supplied to the inlet part 20 is introduced into the cushion 10 through the gas-introduction hole 20a. 
Consequently, the cushion 10 is expanded to the front of the passenger seat at prescribed pressure and speed by means of the gas introduced into the cushion 10, and shock transmitted to the passenger is effectively absorbed by means of the expanded cushion 10, whereby the passenger is protected from injury when a collision of the vehicle occurs.
In the conventional passenger air bag system, however, the expanding stress of the cushion 10 is applied to the first sewing part 28, and simultaneously the stress caused from the expansion of the cushion 10 is applied to the second sewing part 30, when the cushion 10 is expanded by means of the gas discharged from the inflator 6 due to the collision of the vehicle.
At this time, the stress applied to the first sewing part 28 and the stress applied to the second sewing part 30 are concentrated at the sides A of one end of the tether 26 where the first sewing part 28 and the second sewing part 30 intersect each other.
When the stresses are concentrated at the parts A where the first sewing part 28 and the second sewing part 30 intersect each other as described above, the stress applied to the first sewing part 28 and the stress applied to the second sewing part 30 are increased with the result that the parts A where the first sewing part 28 and the second sewing part 30 intersect each other are torn when the cushion 10 is expanded. As a result, the cushion may be easily damaged.
In the case that the cushion 10 is damaged during the expansion of the cushion 10, the passenger air bag system cannot function. Consequently, shock transmitted to the passenger is not effectively absorbed when a collision of the vehicle occurs, and thus the passenger is not protected from injury.